The present invention generally relates to the field of gas turbine engines. In particular, the invention relates to an engine casing for a jet turbine engine.
Turbofans are a type of gas turbine engine commonly used in aircraft, such as jets. The turbofan generally includes a high and a low pressure compressor, a high and a low pressure turbine, a high pressure rotatable shaft, a low pressure rotatable shaft, a fan, and a combuster. The high-pressure compressor (HPC) is connected to the high pressure turbine (HPT) by the high pressure rotatable shaft, together acting as a high pressure system. Likewise, the low pressure compressor (LPC) is connected to the low pressure turbine (LPT) by the low pressure rotatable shaft, together acting as a low pressure system. The low pressure rotatable shaft is housed within the high pressure shaft and is connected to the fan such that the HPC, HPT, LPC, LPT, and high and low pressure shafts are coaxially aligned.
Outside air is drawn into the jet turbine engine by the fan and the HPC, which increases the pressure of the air drawn into the system. The high-pressure air then enters the combuster, which burns fuel and emits the exhaust gases. The HPT directly drives the HPC using the exhaust gases to rotate the high pressure shaft. The LPT uses the exhaust generated in the combuster to turn the low pressure shaft, which powers the LPC and the fan. The fan continually brings air into the system. The air brought in by the fan bypasses the HPT and LPT and acts to increase the engine's thrust, driving the jet forward.
In order to support the high and low pressure systems, bearings are located within the jet turbine engine to help distribute the load created by the high and low pressure systems. The bearings are connected to an engine casing that houses a mid-turbine frame located between the HPT and the LPT by bearing support structures. The bearing support structures can be, for example, bearing cones. The loads from the bearing support structures are transferred to the engine casing through the mid-turbine frame. Decreasing the weight of the engine casing can significantly increase the efficiency of the jet turbine engine and the jet itself.